OT (sorta; but still applicable to Jags) -- 12 Volt Battery Capacity

In trouble-shooting my no-start situation on my 1965 Riviera Gran Sport, I have noticed my battery – when cold – (what else would I have?) reads 14.65 volts.
OK – I have since learned a 12 volt battery consists of 6 cells each of 2.2 volts, therefore it is really a 13.2 volt battery (one site said each cell is 2.15 volts - therefore a 12.9 volt battery).

So – why do I have a 14.65 reading?? This even after cranking the starter for a protracted period.


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Because you’re using a very inaccurate meter? A lead acid battery should NEVER read that high, unless it is being charged. Normal no load voltage will be about 12.8V when fully charged.

Ray L.

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Ray – I have a Blue Point digital Multi-Meter. Before I test the battery the display shows 0.000
Maybe I need to change the battery/ies?

Now – I did buy it years (8 to 12) ago to build my tool chest . . .

Try it on a battery in another car and see what it reads.

John – you hit on a key factor; I think I put a ton of trust in a name-brand device (Blue Point MT586 MultiMate) that is proving unwarranted. To wit:

All reading taken on stone cold cars within 5 minutes of each other:
15.57 Volts in 62 TBird with Super Start battery installed in June 2017
15.25 Volts in 03 MB ML350 with MB Battery installed May 2019
15.29 Volts in 65 Buick Riviera with Super Start battery of unknown vintage.

Back to the drawing board – especially since one of the trouble shooting tests was to record voltage with a jumper betw battery and coil Neg posts. While cranking the car, the voltage ought not drop below 10 volts; I recorded 11.9 on what is now a very suspect measuring device.


Go buy yourself a Fluke meter. It won’t cost much (maybe $60?), and it will last a lifetime. I’m still using the Fluke 76 I bought in 1989, and it still works perfectly.

Ray L.


Who carries it?
Auto Zone?
Other . . .

Never Mind

Seems Lowe’s carries Fluke

Ditto: Flukes are da bom!

Had mine since 1985.

Just back from <owe’s with Fluke in hand

14.5 volts pre-start (try) dead cold
9.7-9.8 volts during cranking test with jumper from Neg coil to Neg btry (minimum per MSD = 10)
14.3 volts post-start trial

Much more logical numbers

PS - Ray: check your calendar. The basic (only two cable plug-ins) Fluke was $140. Where ya gettin’ yours for $60??

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And just a quick note and dumb question. Did you try your blue point with a new battery in the meter ? Many DVMs become highly inaccurate when the batt is low.
Even so cant go wrong w a good Fluke I own 3 , for dif purposes and my scopemeter 123 had for 10 years. (And about 6 rechargeable batteries later ) its still going strong.

I hope you’ll get your money back on the Snap-On tester.

My old satellite building company transitioned to ISO 9001 back in 1990’s and had its own in-house calibration dept. Accuracy results are only as good as the tools being used. They went as far as to gather our Engr. tape measures every three months to inspect them and tag them valid.

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I rely on my “el Cheapo” HF meters. digital, analog and inductive…

Been watching a lot of You Tube J.C. Smith, somewhere in Ohio. does a lot with old big trucks. Uses the HF meter with success…

Carl .


What you’re reporting still makes no sense… What are you using to CHARGE those Batteries? The open-circuit terminal voltage of a 12V lead-acid battery should NEVER be anywhere near 14V. That voltage should be present only when it is being charged at a pretty high rate, and at elevated temperature. Are you measuring WITH a battery charger connected? Immediately (as in seconds) AFTER disconnecting a charger? That reading would not be surprising with the engine running and the alternator charging, but I see no way it can happen with NOTHING connected to the battery, unless perhaps the battery has been massively over-charged.

Ray L.
Ray L.

Agreed: I am puzzled, if this is an open battery measurement.

Disconnect battery,Fully charge,then measure next day.

Just as a point of reference the battery for my E-Type has been sitting on a float charger for several weeks and reads 13.13 Vdc (2.19 Vdc per cell) @~ 85 F using my Fluke 115 DVM (after disconnecting the float charger).

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Paul – not bloody likely. I bought the blue Point multimeter at least 10-12 years ago from an eBay vendor whose name has long since been forgotten,

Ray and all others

My apologies for either fat figures or bad eye-sight or misreading my own notes (or all the above). I just now checked the voltage on my battery in the 65 Rivi: 12.4 Volts

All is well. My battery is not about to explore nor is it a magical, mystical super-secret new development in battery technology.


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